Full-text Search applied on a View

Dear all,

I'm using MS SQL Server 2005 and i have a full-text search issue;
Let's say i have table1, table2 and table 3; for each, some full-text
indices have been created.
The issue is that i created a view which joined the three tables and i
attempted to perform a full-text search on that view, but that resulted
in an error indicating that a "unique column" is required for that
view.

Indeed, table1, table2 and table3 are linked together with many to many
relationships so that there are other weak entities between them, for
such duplications are allowed.

Hence, the view would show duplicate PK's.
How do i perform a full-text search on a view as described above?

Best regards